Process

ABSTRACT

The invention provides a process for preparing 1,1,1-trifluoro-2,3-dichloropropane (243db), which process comprises contacting 3,3,3-trifluoropropene (1243zf) with chlorine in the presence of a catalyst, wherein the catalyst comprises activated carbon, alumina and/or an oxide of a transition metal.

The invention relates to a process for preparing1,1,1-trifluoro-2,3-dichloropropane. In particular, the inventionrelates to a process for preparing 1,1,1-trifluoro-2,3-dichloropropanefrom carbon tetrachloride and ethylene including the step ofchlorinating 3,3,3-trifluoropropene.

The invention provides a process for preparing1,1,1-trifluoro-2,3-dichloropropane, which process comprises contacting3,3,3-trifluoropropene with chlorine (Cl₂) in the presence of a catalystto produce 1,1,1-trifluoro-2,3-dichloropropane, wherein the catalystcomprises activated carbon, alumina and/or an oxide of a transitionmetal.

The process of the invention provides a surprisingly clean and efficientmeans for preparing 1,1,1-trifluoro-2,3-dichloropropane from3,3,3-trifluoropropene. For example, by using a catalyst comprisingactivated carbon, alumina and/or an oxide of a transition metal, lowertemperatures can be used compared to without the use of such a catalyst.This is believed to result in less by-products and increase yield of1,1,1-trifluoro-2,3-dichloropropane.

1,1,1-trifluoro-2,3-dichloropropane is also known as HFC-243db or just243db. Unless otherwise stated, 1,1,1-trifluoro-2,3-dichloropropane willbe referred to hereinafter as 243db. 3,3,3-trifluoropropene is alsoknown as HFO-1243zf or just 1243zf. Unless otherwise stated,3,3,3-trifluoropropene will be referred to hereinafter as 1243zf.

For the avoidance of doubt, by a catalyst which comprises activatedcarbon, alumina and/or an oxide of a transition metal, we includecatalysts that are essentially only activated carbon, alumina and/or anoxide of a transition metal and catalysts that are activated carbon,alumina and/or an oxide of a transition metal modified, for example, bythe addition of one or more metals (e.g. transition metals) and/orcompounds thereof.

By “activated carbon”, we include any carbon with a relatively highsurface area such as from about 50 to about 3000 m² or from about 100 toabout 2000 m² (e.g. from about 200 to about 1500 m² or about 300 toabout 1000 m²). The activated carbon may be derived from anycarbonaceous material, such as coal (e.g. charcoal), nutshells (e.g.coconut) and wood. Any form of activated carbon may be used, such aspowdered, granulated and pelleted activated carbon. Activated carbonwhich has been modified (e.g. impregnated) by the addition of Cr, Mn,Au, Fe, Sn, Ta, Ti, Sb, Al, Co, Ni, Mo, Ru, Rh, Pd and/or Pt and/or acompound (e.g. a halide) of one or more of these metals may be used.

Alumina which has been modified by the addition of Cr, Mn, Au, Fe, Sn,Ta, Ti, Sb, Al, Co, Ni, Mo, Ru, Rh, Pd and/or Pt and/or a compound (e.g.a halide) of one or more of these metals may be used.

An oxide of a transition metal that has been modified by the addition ofCr, Mn, Au, Fe, Sn, Ta, Ti, Sb, Al, Co, Ni, Mo, Ru, Rh, Pd and/or Ptand/or a compound (e.g. a halide) of one or more of these metals may beused.

A preferred oxide of a transition metal is an oxide of Cr, Ti, V, Zr, orFe. For example, chromia (Cr₂O₃) alone or chromia that has been modifiedby the addition of Zn, Mn, Zr, Ni, Al and/or Mg and/or a compound of oneor more of these metals may be used. Suitable chromia-based catalystsinclude those described in EP-A-0502605, EP-A-0773061, EP-A-957074, WO98/10862 and WO 2006/106353. A preferred chromia-based catalyst is azinc/chromia catalyst.

A preferred group of catalysts are catalysts which comprise activatedcarbon, alumina and/or chromia. Activated carbon is currently apreferred catalyst because it is cheap, readily available, effective androbust. Activated carbon is commercially available, e.g. fromSutcliffe-Speakman.

The process of the invention may be conducted in the vapour and/orliquid phase, preferably in the vapour phase. The process may be carriedin the liquid phase using the 243db product as the solvent. The heat ofreaction in such a process may be removed by boiling off the 243dbproduct/solvent.

Typically, the process is conducted at a temperature of from about −100to about 400° C., such as from about −80 to about 300° C. or −50 toabout 250° C., e.g. from about 0 to about 200° C. or about 50 to about150° C. The process may be conducted at a pressure of from about 0 toabout 30 bara, such as from about 0.1 to about 20 bara or from about 0.5to about 10 bara, e.g. from about 1 to about 5 bara.

The process of the invention can be carried out in any suitableapparatus, such as a static mixer, a tubular reactor, a stirred tankreactor or a stirred vapour-liquid disengagement vessel. Preferably,this or any other apparatus described herein is made from one or morematerials that are resistant to corrosion, e.g. Hastelloy® or Inconel®.The process may be carried out batch-wise or continuously.

Typically, the molar ratio of 1243zf:chlorine in the chlorinationprocess is from about 10:1 to about 1:5, such as from about 5:1 to about1:2, for example from about 3:1 to about 1.5:1 (e.g. about 2.5:1 toabout 1:1).

The chlorination process of the invention may be carried outphotochemically, for example by exposing the reactants to UV radiationof a suitable wavelength, typically from about 190 to about 420 nm (suchas monochromatic radiation, e.g. 254 nm). Any suitable catalyst of theinvention selected from activated carbon, alumina and/or an oxide of atransition metal may be used in the photochemical process. Currentlypreferred catalysts include activated carbon and zinc oxide.

1243zf is commercially available (e.g. from Apollo Scientific Ltd, UK).Alternatively, 1243zf may also be prepared via a synthetic routestarting from the cheap feedstocks carbon tetrachloride (CCl₄) andethylene (see the reaction scheme is set out below).

These two starting materials may be telomerised to produce1,1,1,3-tetrachloropropane (see, for example, J. Am. Chem. Soc. Vol. 70,p 2529, 1948, which is incorporated herein by reference) (also known asHCC-250fb, or simply 250fb).

250fb may then be fluorinated to produce 1243zf and/or1,1,1-trifluoro-3-chloropropane (e.g. using HF, optionally in thepresence of a chromia-containing catalyst, preferably a zinc/chromiacatalyst as described herein). Dehydrohalogenation of1,1,1-trifluoro-3-chloropropane (e.g. using NaOH or KOH) produces1243zf. Alternatively (not shown), 250fb may be dehydrochlorinated to3,3,3-trichloropropene, followed by fluorination to 1243zf.

Thus, in a further aspect of the invention there is provided a processfor preparing 1,1,1-trifluoro-2,3-dichloropropane (243db), which processcomprises:

(a) telomerising ethylene and carbon tetrachloride (CCl₄) to produce1,1,1,3-tetrachloropropane (250fb);(b) converting 250fb to 3,3,3-trifluoropropene; and(c) contacting 3,3,3-trifluoropropene with chlorine (Cl₂) in thepresence of a catalyst to produce 1,1,1-trifluoro-2,3-dichloropropane(1243zf), wherein the catalyst comprises activated carbon, aluminaand/or an oxide of a transition metal.

Step (a) of the above process typically comprises contacting ethylenewith CCl₄ in the liquid and/or vapour phase in presence of a catalystunder conditions suitable to produce 1,1,1,3-tetrachloropropane.

Any suitable catalyst may be used in step (a), such as a catalyst whichcomprises iron, copper and/or peroxide.

Catalysts which comprise peroxide include benzoyl peroxide anddi-t-butyl peroxide. Catalysts which comprise iron include iron powderand ferric/ferrous halides (e.g. chlorides). Catalysts which comprisecopper include salts of copper such as copper halides (e.g. CuCl₂),copper sulphate and/or copper cyanide.

Typically, the catalysts which comprise copper and iron are used with aco-catalyst or ligand. Suitable co-catalysts includetriethylorthoformate (HC(OEt)₃), nitrogen/phosphorus-containing ligands,and/or ammonium/phosphonium salts. Preferred nitrogen-containing ligandsinclude amines (e.g. primary and secondary amines), nitriles and amides.Preferred phosphorus containing ligands include phosphates, phosphites(e.g. triethylphosphite) and phosphines. Preferred ammonium andphosphonium salts include ammonium and phosphonium halides (e.g.chlorides).

The catalyst for step (a) typically is used in an amount from about 0.01to about 50 mol % (e.g. about 0.1 to about 10%), based on the molar sumof carbon tetrachloride and ethylene present. An excess of the carbontetrachloride over ethylene generally is used. For example, the molarratio of CCl₄:C₂H₄ typically is from about 1:1 to about 50:1, such asfrom about 1.1:1 to about 20:1, for example from about 1.2:1 to about10:1 or about 1.5:1 to about 5:1.

The reaction temperature for step (a) typically is within the range offrom 20 to 300° C., preferably from about 30 to about 250° C., such asfrom about 40 to about 200° C., e.g. from about 50 to about 150° C.

The reaction pressure for step (a) typically is within the range of from0 to about 40 bara, preferably from about 1 to about 30 bara.

The reaction time for step (a) generally is from about 1 second to about100 hours, preferably from about 10 seconds to about 50 hours, such asfrom about 1 minute to about 10 hours.

Step (a) can be carried out in any suitable apparatus, such as a staticmixer, a tubular reactor, a stirred tank reactor or a stirredvapour-liquid disengagement vessel. Step (a) may be carried outbatch-wise or continuously. Preferably, the 1,1,1,3-tetrachloropropaneformed in step (a) is purified and/or isolated before it is fluorinatedin step (b). This purification may conveniently be achieved, for exampleby distillation and/or extraction.

The conversion of 1,1,1,3-tetrachloropropane (250fb) to3,3,3-trifluoropropene (1243zf) in step (b) above typically involvesfluorination and dehydrohalogenation sub-steps.

For example, 250fb may be fluorinated to produce a compound of formulaCF₃CH₂CH₂Cl (253fb), followed by dehydrohalogenation of the 253fb toproduce 1243zf. This will be referred to hereinafter as route (b1).

Alternatively, 250fb may be dehydrochlorinated to produce3,3,3-trichloropropene, followed by fluorination to produce 1243zf. Thiswill be referred to hereinafter as route (b2).

Either or both routes (b1) and (b2) may be used to convert1,1,1,3-tetrachloropropane to 3,3,3-trifluoropropene, depending on thechoice of reagents and/or catalysts. The route taken and the number ofsteps involved may depend on factors such as the reaction conditions andthe nature of catalyst employed (if any). Such factors are described inmore detail below.

In route (b1), for example, 250fb may be fluorinated with HF in thepresence of a catalyst to produce 253fb. Any suitable catalyst for HFfluorination may be used, such as compounds comprising aluminium (e.g.alumina-based catalysts) and/or chromium (e.g. chromia-based catalysts,especially zinc/chromia catalysts as described herein) and/or metalhalides such as chlorides or fluorides (e.g. TiCl₄, SnCl₄ or SbF₅)and/or nitrogen-containing bases (e.g. amines and nitrogen-containingheterocycles such as pyridine).

253fb may then be dehydrohalogenated to 1243zf by any suitable method,for example by base-mediated (e.g. using a base comprising alkali oralkaline earth metal hydroxides or amides), thermal or metal catalysed(e.g. zinc/chromia-catalysed) dehydrohalogenation. Thedehydrohalogenation may be conducted in the presence or absence of HF.Suitable reaction conditions for the dehydrohalogenation of the 253fbare described hereinafter in relation to the dehydrohalogenation step(iii) of a compound of formula CF₃CHFCH₂X (wherein X═Cl or F).

The fluorination and dehydrohalogenation reactions in step (b or routeb1) using HF may be conducted simultaneously (i.e. in a one-pot process)or sequentially, optionally with separation/isolation of the 253fb priorto dehydrohalogenation. Preferably, route (b1) is carried out in one-potusing a zinc/chromia catalyst.

In route (b2), the dehydrochlorination and fluorination reactions may becarried out under substantially the same reaction conditions, i.e. in aone-pot process. Thus, 250fb may be contacted with HF in the presence ofa catalyst to produce 1243zf, typically via 1,1,1,3-tetrafluoropropane.Suitable catalysts include compounds comprising aluminium (e.g. aluminaor aluminium fluoride) and/or chromium (e.g. chromia-based catalysts,especially zinc/chromia catalysts as described herein), and/or metalhalides such as chlorides or fluorides (e.g. TaF₅, TiCl₄, SnCl₄, SbCl₅or SbF₅) and/or nitrogen-containing bases (e.g. amines and nitrogencontaining heterocycles such as pyridine). Examples of catalystscompounds comprising aluminium include AlF₃, optionally mixed with oneor more transition metal compounds.

Although HF is described as a suitable fluorination agent for step (b),any suitable fluorination agent may be used. For example, in analternative embodiment, 1243zf may be produced in one pot by treating250fb with NaF, KF, or amine:HF complexes such as Olah's reagent.

Typically, step (b) is carried out at a temperature of about 20 to about500° C. For example, when using KF or Olah's reagent (pyrindiniumpoly(HF)), temperatures of about 50 to about 200° C. may be used.Alternatively, when using HF, higher temperatures may be employed, suchas from about 100 to about 500° C. (e.g. about 120 to about 400° C. orabout 150 to about 250° C.).

The temperature used may vary depending on the nature of the catalystemployed. For example, when a nitrogen-containing base is used, thepreferred temperature may range from about 100 to about 250° C., whereaswhen a catalyst based on a compound of aluminium is employed, thepreferred temperature may vary from about 200 to about 350° C. When azinc/chromia catalyst is used for step (ii), the temperature typicallyranges from about 150 to about 400° C., such as from about 150 to about350° C., e.g. from about 150 to about 300° C. or from about 150 to about250° C.

The reaction pressure for step (b) typically is within the range of from0 to about 30 bara, preferably from about 1 to about 20 bara.

An excess of the fluorination agent is generally used in step (b),whether the 1243zf is produced via route (b1) or route (b2). Forexample, when using HF as the fluorination agent, a molar ratio ofHF:organics of from about 1:1 to about 100:1, such as from about 3:1 toabout 50:1, e.g. from about 6:1 to about 30:1 may be used.

The reaction time for step (b) generally is from about 1 second to about100 hours, preferably from about 10 seconds to about 50 hours, such asfrom about 1 minute to about 10 hours. In a continuous process, typicalcontact times of the catalyst with the reagents is from about 1 to about1000 seconds, such from about 1 to about 500 seconds or about 1 to about300 seconds or about 1 to about 50, 100 or 200 seconds.

Step (b) can be carried out in any suitable apparatus, such as a staticmixer, a tubular reactor, a stirred tank reactor or a stirredvapour-liquid disengagement vessel. Step (b) may be carried outbatch-wise or continuously. Preferably, the 1243zf formed in step (b) ispurified and/or isolated before it is chlorinated in step (c). Thispurification may conveniently be achieved, for example by distillationand/or extraction.

Step (b) is described in more detail towards the end of thisspecification in a further embodiment denoted the 1243zf preparationprocess.

The conditions for step (c) typically will be as defined above in thefirst embodiment of the invention.

In a preferred aspect of the invention, the 243db formed by theprocesses described herein is fluorinated to produce a compound offormula CF₃CHFCH₂X, wherein X is Cl or F. Thus, the invention provides aprocess for preparing a compound of formula CF₃CHFCH₂X, wherein X is Clor F, the process comprising (i) contacting 3,3,3-trifluoropropene(1243zf) with chlorine (Cl₂) in the presence of a catalyst comprisingactivated carbon, alumina and/or an oxide of a transition metal toproduce 1,1,1-trifluoro-2,3-dichloropropane (243db), and (ii) contactingthe 243db with hydrogen fluoride (HF) in the presence of a fluorinationcatalyst to produce the compound of formula CF₃CHFCH₂X.

Any suitable fluorination catalyst may be used in step (ii), includingbut not limited to catalysts comprising activated carbon, alumina and/oran oxide of a transition metal (as described hereinbefore in relation tothe chlorination step (i)) and supported (e.g. on carbon) or unsupportedlewis acid metal halides, including TaX₅, SbX₅, SnX₄, TiX₄, FeCl₃, NbX₅,VX₅, AlX₃ (wherein X═F or Cl).

Catalysts comprising chromia are a preferred group of catalysts for usein step (ii). For example, chromia (Cr₂O₃) that has been modified by theaddition of Zn, Mn, Zr, Ni, Al and/or Mg and/or a compound of one ormore of these metals may be used. Suitable chromia-based catalystsinclude those described in EP-A-0502605, EP-A-0773061, EP-A-957074, WO98/10862 and WO 2006/106353. A preferred chromia-based catalyst is azinc/chromia catalyst.

By the term “zinc/chromia catalyst” we mean any catalyst comprisingchromium or a compound of chromium and zinc or a compound of zinc. Suchcatalysts are known in the art, see for example EP-A-0502605,EP-A-0773061, EP-A-0957074 and WO 98/10862, which are incorporated byreference herein. However, the present inventors have surprisingly foundthat zinc/chromia catalysts may be used promote the dehydrohalogenationof 243db to produce 1233xf, and/or the fluorination of 1233xf to producethe compound of formula CF₃CFXCH₃, and/or the dehydrohalogenation of thecompound of formula CF₃CFXCH₃ to produce 1234yf.

Typically, the chromium or compound of chromium present in thezinc/chromia catalysts of the invention is an oxide, oxyfluoride orfluoride of chromium such as chromium oxide.

The total amount of the zinc or a compound of zinc present in thezinc/chromia catalysts of the invention is typically from about 0.01% toabout 25%, preferably 0.1% to about 25%, conveniently 0.01% to 6% zinc,and in some embodiments preferably 0.5% by weight to about 25% by weightof the catalyst, preferably from about 1 to 10% by weight of thecatalyst, more preferably from about 2 to 8% by weight of the catalyst,for example about 4 to 6% by weight of the catalyst.

In other embodiments, the catalyst conveniently comprises 0.01% to 1%,more preferably 0.05% to 0.5% zinc.

The preferred amount depends upon a number of factors such as the natureof the chromium or a compound of chromium and/or zinc or a compound ofzinc and/or the way in which the catalyst is made. These factors aredescribed in more detail hereinafter.

It is to be understood that the amount of zinc or a compound of zincquoted herein refers to the amount of elemental zinc, whether present aselemental zinc or as a compound of zinc.

The zinc/chromia catalysts used in the invention may include anadditional metal or compound thereof. Typically, the additional metal isa divalent or trivalent metal, preferably selected from nickel,magnesium, aluminium and mixtures thereof. Typically, the additionalmetal is present in an amount of from 0.01% by weight to about 25% byweight of the catalyst, preferably from about 0.01 to 10% by weight ofthe catalyst. Other embodiments may comprise at least about 0.5% byweight or at least about 1% weight of additional metal.

The zinc/chromia catalysts used in the present invention may beamorphous. By this we mean that the catalyst does not demonstratesubstantial crystalline characteristics when analysed by, for example,X-ray diffraction.

Alternatively, the catalysts may be partially crystalline. By this wemean that from 0.1 to 50% by weight of the catalyst is in the form ofone or more crystalline compounds of chromium and/or one or morecrystalline compounds of zinc. If a partially crystalline catalyst isused, it preferably contains from 0.2 to 25% by weight, more preferablyfrom 0.3 to 10% by weight, still more preferably from 0.4 to 5% byweight of the catalyst in the form of one or more crystalline compoundsof chromium and/or one or more crystalline compounds of zinc.

During use in a fluorination/dehydrohalogenation reaction the degree ofcrystallinity may change. Thus it is possible that a catalyst of theinvention that has a degree of crystallinity as defined above before usein a fluorination/dehydrohalogenation reaction and will have a degree ofcrystallinity outside these ranges during or after use in afluorination/dehydrohalogenation reaction.

The percentage of crystalline material in the catalysts of the inventioncan be determined by any suitable method known in the art. Suitablemethods include X-ray diffraction (XRD) techniques. When X-raydiffraction is used the amount of crystalline material such as theamount of crystalline chromium oxide can be determined with reference toa known amount of graphite present in the catalyst (eg the graphite usedin producing catalyst pellets) or more preferably by comparison of theintensity of the XRD patterns of the sample materials with referencematerials prepared from suitable internationally recognised standards,for example NIST (National Institute of Standards and Technology)reference materials.

The zinc/chromia catalysts of the invention typically have a surfacearea of at least 50 m²/g and preferably from 70 to 250 m²/g and mostpreferably from 100 to 200 m²/g before it is subjected to pre-treatmentwith a fluoride containing species such as hydrogen fluoride or afluorinated hydrocarbon. During this pre-treatment, which is describedin more detail hereinafter, at least some of the oxygen atoms in thecatalyst are replaced by fluorine atoms.

The zinc/chromia catalysts of the invention typically have anadvantageous balance of levels of activity and selectivity. Preferably,they also have a degree of chemical robustness that means that they havea relatively long working lifetime. The catalysts of the inventionpreferably also have a mechanical strength that enables relatively easyhandling, for example they may be charged to reactors or discharged fromreactors using known techniques.

The zinc/chromia catalysts of the invention may be provided in anysuitable form known in the art. For example, they may be provided in theform of pellets or granules of appropriate size for use in a fixed bedor a fluidised bed. The catalysts may be supported or unsupported. Ifthe catalyst is supported, suitable supports include AlF₃, fluorinatedalumina or activated carbon.

The zinc/chromia catalysts of the invention include promoted forms ofsuch catalysts, including those containing enhanced Lewis and/orBrönsted acidity and/or basicity.

The amorphous catalysts which may be used in the present invention canbe obtained by any method known in the art for producing amorphouschromia-based catalysts. Suitable methods include co-precipitation fromsolutions of zinc and chromium nitrates on the addition of ammoniumhydroxide. Alternatively, surface impregnation of the zinc or a compoundthereof onto an amorphous chromia catalyst can be used.

Further methods for preparing the amorphous zinc/chromia catalystsinclude, for example, reduction of a chromium (VI) compound, for examplea chromate, dichromate, in particular ammonium dichromate, to chromium(III), by zinc metal, followed by co-precipitation and washing; ormixing as solids, a chromium (VI) compound and a compound of zinc, forexample zinc acetate or zinc oxalate, and heating the mixture to hightemperature in order to effect reduction of the chromium (VI) compoundto chromium (III) oxide and oxidise the compound of zinc to zinc oxide.

The zinc may be introduced into and/or onto the amorphous chromiacatalyst in the form of a compound, for example a halide, oxyhalide,oxide or hydroxide depending at least to some extent upon the catalystpreparation technique employed. In the case where amorphous catalystpreparation is by impregnation of a chromia, halogenated chromia orchromium oxyhalide, the compound is preferably a water-soluble salt, forexample a halide, nitrate or carbonate, and is employed as an aqueoussolution or slurry. Alternatively, the hydroxides of zinc and chromiummay be co-precipitated (for example by the use of a base such as sodiumhydroxide or ammonium hydroxide) and then converted to the oxides toprepare the amorphous catalyst. Mixing and milling of an insoluble zinccompound with the basic chromia catalyst provides a further method ofpreparing the amorphous catalyst precursor. A method for makingamorphous catalyst based on chromium oxyhalide comprises adding acompound of zinc to hydrated chromium halide.

The amount of zinc or a compound of zinc introduced to the amorphouscatalyst precursor depends upon the preparation method employed. It isbelieved that the working catalyst has a surface containing cations ofzinc located in a chromium-containing lattice, for example chromiumoxide, oxyhalide, or halide lattice. Thus the amount of zinc or acompound of zinc required is generally lower for catalysts made byimpregnation than for catalysts made by other methods such asco-precipitation, which also contain the zinc or a compound of zinc innon-surface locations.

Any of the aforementioned methods, or other methods, may be employed forthe preparation of the amorphous catalysts which may be used in theprocess of the present invention.

The zinc/chromia catalysts described herein are typically stabilised byheat treatment before use such that they are stable under theenvironmental conditions that they are exposed to in use. Thisstabilisation is often a two-stage process. In the first stage, thecatalyst is stabilised by heat treatment in nitrogen or a nitrogen/airenvironment. In the art, this stage is often called “calcination”.Fluorination catalysts are then typically stabilised to hydrogenfluoride by heat treatment in hydrogen fluoride. This stage is oftentermed “pre-fluorination”.

By careful control of the conditions under which these two heattreatment stages are conducted, crystallinity can be induced into thecatalyst to a controlled degree.

For example, an amorphous catalyst may be heat treated at a temperatureof from about 300 to about 600° C., preferably from about 400 to 600°C., more preferably from 500 to 590° C., for example 520, 540, 560 or580° C. for a period of from about 1 to about 12 hours, preferably forfrom about 2 to about 8 hours, for example about 4 hours in a suitableatmosphere. Suitable atmospheres under which this heat treatment can beconducted include an atmosphere of nitrogen or an atmosphere having anoxygen level of from about 0.1 to about 10% v/v in nitrogen. Otheroxidizing environments could alternatively be used. For example,environments containing suitable oxidizing agents include, but are notlimited to, those containing a source of nitrate, CrO₃ or O₂ (forexample air). This heat treatment stage can be conducted in addition toor instead of the calcining stage that is typically used in the priorart to produce amorphous catalysts.

Conditions for the pre-fluorination stage can be selected so that theydo not substantially introduce crystallinity into the catalyst. This maybe achieved by heat treatment of the catalyst precursor at a temperatureof from about 200 to about 500° C., preferably from about 250 to about400° C. at atmospheric or super atmospheric pressure for a period offrom about 1 to about 16 hours in the presence of hydrogen fluoride,optionally in the presence of another gas such as nitrogen.

Conditions for the pre-fluorination stage can be selected so that theyinduce a change in the crystallinity of the catalyst or so that they donot induce such a change. The present inventors have found that heattreatment of the catalyst precursor at a temperature of from about 250to about 500° C., preferably from about 300 to about 400° C. atatmospheric or super atmospheric pressure for a period of from about 1to about 16 hours in the presence of hydrogen fluoride, optionally inthe presence of another gas such as air, can produce a catalyst in whichthe crystallinity is as defined above, for example from 0.1 to 8.0% byweight of the catalyst (typically from 0.1 to less than 8.0% by weightof the catalyst) is in the form of one or more crystalline compounds ofchromium and/or one or more crystalline compounds of the at least oneadditional metal.

The skilled person will appreciate that by varying the conditionsdescribed above, such as by varying the temperature and/or time and/oratmosphere under which the heat treatment is conducted, the degree ofcrystallinity of the catalyst may be varied. Typically, for example,catalysts with higher degrees of crystallinity (e.g. from 8 to 50% byweight of the catalyst) may be prepared by increasing the temperatureand/or increasing the calcination time and/or increasing the oxidisingnature of the atmosphere under which the catalyst pre-treatment isconducted.

The variation of catalyst crystallinity as a function of calcinationtemperature, time and atmosphere is illustrated by the following tableshowing a series of experiments in which 8 g samples of a 6%zinc/chromia catalyst were subjected to calcination across a range ofconditions and the level of crystallinity induced determined by X-Raydiffraction.

Calcination Calcination Atmosphere % Cryst Time Temperature nitrogen:airCr₂O₃ (t, hrs) (T, ° C.) (D, v/v) Content 4 400.0 15 1 4 400.0 15 1 2450.0 20 9 6 350.0 20 0 2 450.0 10 18 2 350.0 10 0 6 450.0 20 20 6 350.010 0 6 450.0 10 30 4 400.0 15 1 2 350.0 20 0

The pre-fluorination treatment typically has the effect of lowering thesurface area of the catalyst. After the pre-fluorination treatment thecatalysts of the invention typically have a surface area of 20 to 200m²/g, such as 50 to 150 m²/g, for example less than about 100 m²/g.

In use, the zinc/chromia catalyst may be regenerated or reactivatedperiodically by heating in air at a temperature of from about 300° C. toabout 500° C. Air may be used as a mixture with an inert gas such asnitrogen or with hydrogen fluoride, which emerges hot from the catalysttreatment process and may be used directly in fluorination processesemploying the reactivated catalyst. Alternatively, the catalyst can beregenerated continuously whilst in use by introducing an oxidising gasinto the reactor e.g. oxygen or chlorine.

Step (ii) can be carried out in any suitable apparatus, such as a staticmixer, a tubular reactor, a stirred tank reactor or a stirredvapour-liquid disengagement vessel. Step (ii) may be carried outbatch-wise or continuously and in the gas or liquid phase.

Step (ii) may be carried out simultaneously with step (i). In otherwords, the process may comprise contacting 3,3,3-trifluoropropene(1243zf) with chlorine (Cl₂) and HF in the presence of a catalystcomprising activated carbon, alumina and/or an oxide of a transitionmetal to produce a compound of formula CF₃CHFCH₂X, wherein X is Cl or F.Thus, in this process, the catalyst based on activated carbon, aluminaand/or an oxide of a transition metal acts as both a chlorination andfluorination catalyst.

When steps (i) and (ii) are carried out simultaneously, the processconditions used (e.g. temperature, pressure and molar ratio of1243:chlorine) typically are the same as set out above in relation tothe first aspect of the invention for the chlorination of 1243zf to243db (i.e. step (i)). The preferred temperature for this simultaneousprocess may be somewhat higher than for step (i) alone, such as from 0to about 350° C., e.g. from about 50 to about 300° C.

Typically, when steps (i) and (ii) are carried out simultaneously, HFwill be used in a molar excess compared to the amount of 1243zf and/orchlorine. For example, the molar ratio of HF:1243zf may be in the rangeof from about 1:1 to about 200:1, such as from about 2:1 to about 150:1,e.g. from about 5:1 to about 100:1.

In another aspect of the invention, the hydrofluorination step (ii) maybe carried out subsequent to the chlorination step (i). The 243db formedin step (i) may be purified and/or isolated prior to fluorination instep (ii), e.g. by removal and/or recycling from the reaction vessel ofsome or all of the chlorine and/or 1243zf in step (i). For example, the243db may be separated (e.g. by distillation, condensation and phaseseparation, and/or scrubbing with water or aqueous base) from thechlorine and 1243zf in step (i) and transferred to a different reactionvessel or zone for conducting the fluorination step (ii).

By conducting step (i) and (ii) consecutively and in separate reactionzones or vessels, the reagents, temperature, pressure and type ofcatalyst can be chosen to facilitate the chlorination and fluorinationreactions, respectively, as explained below.

For example, a catalyst based on activated carbon may be preferred instep (i) and a chromia-based (e.g. zinc/chromia) catalyst may bepreferred for step (ii). Alternatively/additionally, photochemicalchlorination may be used in step (i), followed by zinc/chromia catalysedhydrofluorination in step (ii).

Step (i) can be conducted in the absence of HF, or with small amounts ofHF (e.g. in order to prevent and/or retard excessive decompositionand/or coking of the catalyst), whereas a relatively high ratio ofHF:243db can be used in step (ii). For example, a typical molar ratio ofHF:1243zf in step (i) is from about 0.01:1 to about 10:1 (e.g. about 0.1to about 5:1), whereas molar ratio of HF:243db in step (ii) is generallyfrom about 1:1 to about 100:1 (e.g. about 3:1 to about 50:1).

Still further, higher temperature and/or pressure conditions may be usedin the fluorination step (ii) compared to the chlorination step (i).Thus, step (i) may be conducted at a temperature of from about −100 toabout 400° C. (e.g. from about −50 to about 250° C.), whereas step (ii)may be conducted at a temperature of from about 100 to about 380° C.(e.g. from about 200 to about 370° C.). Step (i) may be carried out at apressure of from about 0.1 to about 20 bara (e.g. about 0.5 to about 10bara), whereas step (ii) may be carried out at a pressure of from about5 to about 28 bara (e.g. about 10 to about 25 bara).

Steps (i) and (ii) may both be carried out in the liquid phase or in thevapour phase. Alternatively, steps (i) and (ii) may be carried out inthe liquid phase and vapour phase, respectively.

In another aspect of the invention, the compound of formula CF₃CHFCH₂X(wherein X is Cl or F) may be dehydrohalogenated to produce2,3,3,3-tetrafluoropropene. 2,3,3,3-tetrafluoropropene is also known asHFO-1234yf or 1234yf. Unless otherwise stated,2,3,3,3-tetrafluoropropene will be referred to hereinafter as 1234yf.

Thus the invention provides a process for preparing 1234yf, the processcomprising (i) contacting 3,3,3-trifluoropropene (1243zf) with chlorine(Cl₂) in the presence of a catalyst based on activated carbon, aluminaand/or an oxide of a transition metal to produce1,1,1-trifluoro-2,3-dichloropropane (243db), (ii) contacting the 243dbwith hydrogen fluoride (HF) in the presence of a fluorination catalystto produce a compound of formula CF₃CHFCH₂X, wherein X is Cl or F, and(iii) dehydrohalogenating the compound of formula CF₃CHFCH₂X to produce1234yf.

Unless otherwise stated, as used herein, by the term“dehydrohalogenation” (or dehydrohalogenating), we refer to the removalof hydrogen chloride (HCl) or hydrogen fluoride (HF) from the compoundof formula CF₃CHFCH₂X. Thus the term “dehydrohalogenation” includes“dehydrofluorination” and “dehydrochlorination” of the compound offormula CF₃CHFCH₂X.

Step (iii) of the process defined above may be carried out by anysuitable reaction conditions effective to dehydrohalogenate (i.e.dehydrochlorinate or dehydrofluorinate) the compound of formulaCF₃CHFCH₂X to produce 1234yf. Preferably, the dehydrohalogenation iscarried out in the vapour and/or liquid phase and may be carried out ata temperature of from about −70 to about 1000° C. (e.g. about 0 to about400° C.).

The process may be carried out at atmospheric sub- or super atmosphericpressure, preferably from about 0 to about 30 bara.

The dehydrohalogenation may be induced thermally, may be base-mediatedand/or may be catalysed by any suitable catalyst. Suitable catalystsinclude metal and carbon based catalysts such as those comprisingactivated carbon, main group (e.g. alumina-based catalysts) andtransition metals, such as chromia-based catalysts (e.g. zinc/chromia)or nickel-based catalysts (e.g. nickel mesh).

Step (iii) can be carried out in any suitable apparatus, such as astatic mixer, a stirred tank reactor or a stirred vapour-liquiddisengagement vessel. The process may be carried out batch-wise orcontinuously and in the liquid or gas phase.

One preferred method of effecting the dehydrohalogenation of thecompound of formula CF₃CHFCH₂X to produce 1234yf is by contactingCF₃CHFCH₂X with a catalyst based on chromia such as those described inEP-A-0502605, EP-A-0773061, EP-A-957074, WO 98/10862 and WO 2006/106353(e.g. a zinc/chromia catalyst). Thus, when both steps (ii) and (iii) arecarried out in the presence of a catalyst based on chromia (e.g. azinc/chromia catalyst), they may be carried out in a “one-pot” manner.Alternatively, when both steps (ii) and (iii) are carried out in thepresence of a catalyst comprising chromia, the fluorination anddehydrohalogenation reactions may be carried out in two discrete steps,for example using two or more discrete reaction zones or vessels.

When both steps (ii) and (iii) are carried out in the presence of acatalyst based on chromia, the reaction conditions for each step (ii)and (iii) may be the same (e.g. in a one-pot process) or different.Preferably, the reaction conditions when both steps (ii) and (iii) arecarried out in the presence of a catalyst based on chromia can beselected to be different (e.g. when using two or more discrete reactionzones or vessels) so as to optimise the fluorination anddehydrohalogenation reactions, respectively. This is explained in moredetail below.

Fluorination step (ii) preferably is conducted at a temperature of fromabout 0 to about 390° C., such as from about 100 to about 380° C. orfrom about 200 to about 370° C. (e.g. from about 240 to about 260° C.).When conducted in the presence of a catalyst based on chromia (e.g. azinc/chromia catalyst), step (b) preferably is conducted at atemperature of from about 200 to about 360° C., such as from about 240to about 340° C.

It is currently considered to be advantageous to use a higher pressurein step (ii) (to promote fluorination) than in step (iii) (to promotedehydrohalogenation). Thus, step (ii) preferably is carried out fromabout 5 to about 28 bara, such as from about 10 to about 25 bara (e.g.15 to 20 bara), whereas step (iii) preferably is carried out from about0.01 to about 25 bara or about 0.1 to about 20 bara, such as from about1 to about 10 bara (e.g. 1 to 5 bara).

Fluorination step (ii) is carried out by contacting 243db with HF. Step(iii) of the invention may be carried out in the presence of HF. Forexample residual HF from step (ii) may be present, and/or HF from aseparate feed. Alternatively, step (iii) may be carried out in theabsence of HF, for example following separation of the compound offormula CF₃CHFCH₂X from HF prior to step (iii), and with no additionalco-feed of HF. In certain embodiments it may be desirable to use some HFin order to prevent and/or retard excessive decomposition of the organicfeed and/or coking of the catalyst in step (iii).

When both steps (ii) and (iii) are carried out in the presence of acatalyst based on chromia (e.g. a zinc/chromia catalyst) and HF, themolar ratio of HF:organics can be selected to be different in each stepso as to promote fluorination in step (ii) and dehydrohalogenation instep (iii). For example, the molar ratio of HF:organics (e.g. 243db) instep (ii) preferably is from about 1:1 to about 100:1, such as fromabout 2:1 to about 50:1, for example from about 5:1 to about 40:1 (e.g.from about 10:1 to about 30:1). For step (iii), the molar ratio ofHF:organics (e.g. the compound of formula CF₃CHFCH₂X) preferably is fromabout 0.01:1 to about 50:1, such as from about 0.1:1 to about 40:1, forexample from about 0.5:1 to about 30:1 or about 2:1 to about 15:1 (e.g.from about 5:1 to about 10:1).

Another way of decreasing the concentration of HF in step (iii) relativeto step (ii) (thereby facilitating the fluorination/dehydrohalogenationreactions in these steps) is by adding a diluent gas (e.g. nitrogen) tostep (iii).

Another preferred method of effecting the dehydrohalogenation of thecompound of formula CF₃CHFCH₂X to produce 1234yf is by contactingCF₃CHFCH₂X with a base (base-mediated dehydrohalogenation).

This base-mediated dehydrohalogenation process of step (iii) comprisescontacting the hydro(halo)fluoroalkane with base such as a metalhydroxide or amide (preferably a basic metal hydroxide or amide, e.g. analkali or alkaline earth metal hydroxide or amide).

Unless otherwise stated, as used herein, by the term “alkali metalhydroxide”, we refer to a compound or mixture of compounds selected fromlithium hydroxide, sodium hydroxide, potassium hydroxide, rubidiumhydroxide and caesium hydroxide. Similarly, by the term “alkali metalamide”, we refer to a compound or mixture of compounds selected fromlithium amide, sodium amide, potassium amide, rubidium amide and caesiumamide.

Unless otherwise stated, as used herein, by the term “alkaline earthmetal hydroxide”, we refer to a compound or mixture of compoundsselected from beryllium hydroxide, magnesium hydroxide, calciumhydroxide, strontium hydroxide and barium hydroxide. Similarly, by theterm “alkaline earth metal amide”, we refer to a compound or mixture ofcompounds selected from beryllium amide, magnesium amide, calcium amide,strontium amide and barium amide.

Typically, the base-mediated dehydrohalogenation process of step (iii)is conducted at a temperature of from −50 to 300° C. Preferably, theprocess is conducted at a temperature of from 20 to 250° C., for examplefrom 50 to 200° C. The base-mediated dehydrohalogenation may beconducted at a pressure of from 0 to 30 bara.

The reaction time for the base-mediated dehydrohalogenation process ofstep (iii) may vary over a wide range. However, the reaction time willtypically be in the region of from 0.01 to 100 hours, such as from 0.1to 50 hours, e.g. from 1 to 20 hours.

Of course, the skilled person will appreciate that the preferredconditions (e.g. temperature, pressure and reaction time) for conductingthe base-mediated dehydrohalogenation may vary depending on a number offactors such as the nature of the compound of formula CF₃CHFCH₂X, thebase being employed, and/or the presence of a catalyst etc.

The base-mediated dehydrohalogenation process of step (iii) may becarried out in the presence or absence of a solvent. If no solvent isused, the compound of formula CF₃CHFCH₂X may be passed into or overmolten base or hot base, for example in a tubular reactor. If a solventis used, in some embodiments a preferred solvent is water, although manyother solvents may be used. In some embodiments solvents such asalcohols (e.g. propan-1-ol), diols (e.g. ethylene glycol) and polyolssuch as polyethylene glycol (e.g. PEG200 or PEG300) may be preferred.These solvents can be used alone or in combination. In furtherembodiments, solvents from the class known as polar aprotic solvents maybe preferred. Examples of such polar aprotic solvents include diglyme,sulfolane, dimethylformamide (DMF), dioxane, acetonitrile,hexamethylphosphoramide (HMPA), dimethyl sulphoxide (DMSO) and N-methylpyrrolidone (NMP). The boiling point of the solvent is preferably suchthat it does not generate excessive pressure under reaction conditions.

A preferred base is an alkali metal hydroxide selected from the groupconsisting of lithium hydroxide, sodium hydroxide and potassiumhydroxide, more preferably, sodium hydroxide and potassium hydroxide andmost preferably potassium hydroxide.

Another preferred base is an alkaline earth metal hydroxide selectedfrom the group consisting of magnesium hydroxide and calcium hydroxide,more preferably calcium hydroxide.

The base is typically present in an amount of from 1 to 50 weight %based on the total weight of the components which make up step (iii).Preferably, the base is present in an amount of from 5 to 30 weight %.

The molar ratio of base to compound of formula CF₃CHFCH₂X is typicallyfrom 1:20 to 50:1, preferably from 1:5 to 20:1, for example from 1:2 to10:1.

As mentioned above, the base-mediated dehydrohalogenation may preferablyemploy water as the solvent. Thus, the dehydrohalogenation reaction maypreferably use an aqueous solution of at least one base, such as analkali (or alkaline earth) metal hydroxide, without the need for aco-solvent or diluent. However, a co-solvent or diluent can be used forexample to modify the system viscosity, to act as a preferred phase forreaction by-products, or to increase thermal mass. Useful co-solvents ordiluents include those that are not reactive with or negatively impactthe equilibrium or kinetics of the process and include alcohols such asmethanol and ethanol; diols such as ethylene glycol; ethers such asdiethyl ether, dibutyl ether; esters such as methyl acetate, ethylacetate and the like; linear, branched and cyclic alkanes such ascyclohexane, methylcyclohexane; fluorinated diluents such ashexafluoroisopropanol, perfluorotetrahydrofuran and perfluorodecalin.

The base-mediated dehydrohalogenation of step (iii) is preferablyconducted in the presence of a catalyst. The catalyst is preferably aphase transfer catalyst which facilitates the transfer of ioniccompounds into an organic phase from, for example, a water phase. Ifwater is used as a solvent, an aqueous or inorganic phase is present asa consequence of the alkali metal hydroxide and an organic phase ispresent as a result of the fluorocarbon. The phase transfer catalystfacilitates the reaction of these dissimilar components. While variousphase transfer catalysts may function in different ways, their mechanismof action is not determinative of their utility in the present inventionprovided that they facilitate the dehydrohalogenation reaction. Thephase transfer catalyst can be ionic or neutral and is typicallyselected from the group consisting of crown ethers, onium salts,cryptands and polyalkylene glycols and derivatives thereof (e.g.fluorinated derivatives thereof).

An effective amount of the phase transfer catalyst should be used inorder to effect the desired reaction, influence selectivity to thedesired products or enhance the yield; such an amount can be determinedby limited experimentation once the reactants, process conditions andphase transfer catalyst are selected. Typically, the amount of catalystused relative to the amount of compound of formula CF₃CHFCH₂X present isfrom 0.001 to 20 mol %, such as from 0.01 to 10 mol %, e.g. from 0.05 to5 mol %.

Crown ethers are cyclic molecules in which ether groups are connected bydimethylene linkages. Crown ethers form a molecular structure that isbelieved to be capable of receiving or holding the alkali metal ion ofthe hydroxide and to thereby facilitate the reaction. Particularlyuseful crown ethers include 18-crown-6 (especially in combination withpotassium hydroxide), 15-crown-5 (especially in combination with sodiumhydroxide) and 12-crown-4 (especially in combination with lithiumhydroxide).

Derivatives of the above crown ethers are also useful, such asdibenzyl-18-crown-6, dicyclohexanyl-18-crown-6, dibenzyl-24-crown-8 anddibenzyl-12-crown-4. Other compounds analogous to the crown ethers anduseful for the same purpose are compounds which differ by thereplacement of one or more of the oxygen atoms by other kinds of donoratoms, particularly N or S. Fluorinated derivatives of all the above mayalso be used.

Cryptands are another class of compounds useful in the base-mediateddehydrohalogenation as phase transfer catalysts. These are threedimensional polymacrocyclic chelating agents that are formed by joiningbridgehead structures with chains that contain properly spaced donoratoms. The donor atoms of the bridges may all be O, N, or S, or thecompounds may be mixed donor macrocycles in which the bridge strandscontain combinations of such donor atoms. Suitable cryptands includebicyclic molecules that result from joining nitrogen bridgeheads withchains of (—OCH₂CH₂—) groups, for example as in [2.2.2]cryptand(4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane, availableunder the brand names Kryptand 222 and Kryptofix 222).

Onium salts that may be used as catalysts in the base-mediated processof the step (iii) include quaternary phosphonium salts and quaternaryammonium salts, which may be represented by the formulae R¹R²R³R⁴P⁺Z⁻and R¹R²R³R⁴N⁺Z⁻, respectively. In these formulae, each of R¹, R², R³and R⁴ typically represent, independently, a C₁₋₁₀ alkyl group, an arylgroup (e.g. phenyl, naphthyl or pyridinyl) or an arylalkyl group (e.g.benzyl or C₁₋₁₀ alkyl-substituted phenyl), and Z⁻ is a halide or othersuitable counterion (e.g. hydrogen sulphate).

Specific examples of such phosphonium salts and quaternary ammoniumsalts include tetramethylammonium chloride, tetramethylammonium bromide,benzyltriethylammonium chloride, methyltrioctylammonium chloride(available commercially under the brands Aliquat 336 and Adogen 464),tetra-n-butylammonium chloride, tetra-n-butylammonium bromide,tetra-n-butylammonium hydrogen sulphate, tetra-n-butylphosphoniumchloride, tetraphenylphosphonium bromide, tetraphenylphosphoniumchloride, triphenylmethylphosphonium bromide andtriphenylmethylphosphonium chloride. Benzyltriethylammonium chloride ispreferred for use under strongly basic conditions.

Other useful onium salts include those exhibiting high temperaturestabilities (e.g. up to about 200° C.), for example4-dialkylaminopyridinium salts, tetraphenylarsonium chloride,bis[tris(dimethylamino)phosphine]iminium chloride andtetrakis[tris(dimethylamino)phosphinimino]phosphonium chloride. Thelatter two compounds are also reported to be stable in the presence ofhot, concentrated sodium hydroxide and, therefore, can be particularlyuseful.

Polyalkylene glycol compounds useful as phase transfer catalysts may berepresented by the formula R⁶O(R⁵O)_(m)R⁷ wherein R⁵ is a C₁₋₁₀ alkylenegroup, each of R⁶ and R⁷ are, independently H, a C₁₋₁₀ alkyl group, anaryl group (e.g. phenyl, naphthyl or pyridinyl) or an arylalkyl group(e.g. benzyl or C₁₋₁₀ alkyl-substituted phenyl), and m is an integer ofat least 2. Preferable both R⁶ and R⁷ are the same, for example they mayboth by H.

Such polyalkylene glycols include diethylene glycol, triethylene glycol,tetraethylene glycol, pentaethylene glycol, hexaethylene glycol,diisopropylene glycol, dipropylene glycol, tripropylene glycol,tetrapropylene glycol and tetramethylene glycol, monoalkyl glycol etherssuch as monomethyl, monoethyl, monopropyl and monobutyl ethers of suchglycols, dialkyl ethers such as tetraethylene glycol dimethyl ether andpentaethylene glycol dimethyl ether, phenyl ethers, benzyl ethers ofsuch glycols, and polyalkylene glycols such as polyethylene glycol(average molecular weight about 300) and polyethylene glycol (averagemolecular weight about 400) and the dialkyl (e.g. dimethyl, dipropyl,dibutyl)ethers of such polyalkylene glycols.

Combinations of phase transfer catalysts from within one of the groupsdescribed above may also be useful as well as combinations or mixturesfrom more than one group. Crown ethers and quaternary ammonium salts arethe currently preferred groups of catalysts, for example 18-crown-6 andits fluorinated derivatives and benzyltriethylammonium chloride.

In a further aspect of the invention, 1234yf may be prepared startingfrom the above-described chlorination of 1243zf to 243db, but then froma different route from 243db than defined above in steps (ii) and (iii).This alternative route involves the dehydrochlorination of 243db toproduce 3,3,3-trifluoro-2-chloro-prop-1-ene (CF₃CCl═CH₂, 1233xf). 1233xfmay then be fluorinated to produce a compound of formula CF₃CFXCH₃(wherein X═Cl, or F), which may then be dehydrohalogenated to produce1234yf.

Thus there is provided a process for preparing 1234yf comprising (w)contacting 1243zf with Cl₂ in the presence of a catalyst comprisingactivated carbon, alumina and/or an oxide of a transition metal toproduce 243db, (x) converting 243db to3,3,3-trifluoro-2-chloro-prop-1-ene (CF₃CCl═CH₂), (y) contactingCF₃CCl═CH₂ with a fluorinating agent to produce a compound of formulaCF₃CFXCH₃, wherein X═Cl or F, and (z) dehydrohalogenating the compoundof formula CF₃CFXCH₃ to produce 1234yf.

Step (w) corresponds to the process described hereinbefore for thechlorination of 1243zf to 243db, e.g. step (i).

The above process comprising steps (w), (x), (y) and (z) may be carriedout batch-wise or continuously. Each step (w), (x), (y) and (z) mayindependently be carried out batch-wise or continuously.

3,3,3-trifluoro-2-chloro-prop-1-ene (CF₃CCl═CH₂) is also known asHFO-1233xf or 1233xf. Unless otherwise stated, this compound will bereferred to as 1233xf. The compound of formula CF₃CFXCH₂ may beCF₃CFClCH₃, which is also known as HCFC-244cb or 244cb, or CF₃CF₂CH₃,which is also known as HFC-245cb or 245cb. Unless otherwise stated,these compounds will be referred to as 244cb and 245cb, respectively.

Step (x) of the invention comprises converting 243db to 1233xf. Thus,step (x) involves the dehydrochlorination of 243db to produce 1233xf.Step (x) preferably is carried out in a first reactor in the presence ofa first catalyst. This reaction may be carried out in the liquid phaseor the gas phase, preferably the gas phase.

The catalyst used in step (x) may be any suitable catalyst that iseffective to dehydrochlorinate 243db. Preferred catalysts are thosecomprising activated carbon, alumina and/or an oxide of a transitionmetal. Such catalysts are described in more detail above in relation tothe conversion of 1243zf to 243db. A further group of preferredcatalysts for step (x) are supported (e.g. on carbon) or unsupportedlewis acid metal halides, including TaX₅, SbX₅, SnX₄, TiX₄, FeCl₃, NbX₅,VX₅, AlX₃ (wherein X═F or Cl).

A preferred group of catalysts for step (x) are catalysts which compriseactivated carbon, alumina and/or chromia. Catalysts based on chromiacurrently are particularly preferred. A preferred chromia-based catalystis a zinc/chromia catalyst. Catalysts comprising activated carboncurrently are also particularly preferred. The use of the samecatalyst(s) for steps (w) and (x) allows these steps to be carried outsimultaneously in “one-pot”.

The catalyst in step (x) may be used in an amount of from about 0.01 toabout 50% by weight, such as from about 0.1 to about 30%, for examplefrom about 0.5 to about 20%, based on the weight of 243db.

It is preferable for step (x) to be carried out in the presence ofhydrogen fluoride (HF). For example, when alumina or an oxide of atransition metal is used as a catalyst in step (e.g. a chromia-basedcatalyst such as zinc/chromia), HF may be used to prevent and/or retardexcessive decomposition of the catalyst. Step (x) may also be carriedout in the presence of Cl₂, for example when steps (w) and (x) arecarried out in simultaneously in a one-pot conversion of 1243zf to1233xf.

Step (x) may be carried out at a temperature of from about −70 to about450° C. and at atmospheric, sub- or super-atmospheric pressure,preferably from about 0 to about 30 bara.

Preferably, step (x) is conducted at a temperature of from about 0 toabout 390° C., such as from about 100 to about 380° C. or from about 200to about 370° C. (e.g. from about 240 to about 260° C.).

Step (x) preferably is carried out at a pressure of from about 0.01 toabout 25 bara or about 0.1 to about 20 bara, such as from about 1 toabout 10 bara (e.g. 1 to 5 bara).

Step (y) of the invention comprises contacting CF₃CCl═CH₂ with afluorinating agent to produce a compound of formula CF₃CFXCH₃, whereinX═Cl or F. Thus, step (y) involves the fluorination of 1233xf to produce244cb and/or 245cb. Step (y) preferably is carried out in a secondreactor in the presence of a second catalyst. This reaction may becarried out in the liquid phase or the gas phase, preferably the liquidphase.

Any suitable fluorinating agent may be used in step (y), including anysuitable source of nucleophilic fluoride, optionally in a polar aproticor protic solvent. Examples of suitable fluorinating agents include HF,NaF, KF and amine:HF complexes such as Olah's reagent. HF is a preferredfluorinating agent, as is KF in a polar aprotic or protic solvent.

The catalyst used in step (y) may be any suitable catalyst that iseffective to fluorinate 1233xf. Preferred catalysts are those comprisingactivated carbon, alumina and/or an oxide of a transition metal and/orsupported or unsupported lewis acid metal halides as described above inrelation to the chlorination of 1243zf to 243db and step (x).

Preferred catalysts for step (y) are those which comprise chromia(particularly for vapour phase reactions) and lewis acid metal halidecatalysts (particularly for liquid phase reactions). A preferredchromia-based catalyst for use in step (y) is a zinc/chromia catalyst.The same catalyst may be used for step (x) and (y), e.g. a chromia-basedcatalyst.

Typically, step (y) is conducted at a temperature of from about −100 toabout 400° C. and a pressure of 0 to about 50 bara.

If step (y) is carried out in the liquid phase, it preferably isconducted at a temperature of from about −50 to about 250° C., such asfrom about 0 to about 200° C. or from about 10 to about 150° C. (e.g.from about 50 to about 100° C.), and conducted at a pressure of fromabout 1 to about 50 bara or about 5 to about 40 bara, such as from about10 to about 30 bara (e.g. 15 to 25 bara).

If step (y) is carried out in the gas phase, it preferably is conductedat a temperature of from about 0 to about 390° C., such as from about100 to about 350° C. or from about 200 to about 300° C., and conductedat a pressure of from about 0.1 to about 30 bara or about 0.5 to about25 bara, such as from about 1 to about 20 bara (e.g. 5 to 15 bara).

Steps (x) and (y) preferably are carried out in separate first andsecond reactors, respectively. Any suitable apparatus may be used as areactor for steps (x) and (y), such as a static mixer, a stirred tankreactor or a stirred vapour-liquid disengagement vessel.

It is believed that there are advantages associated with the use ofseparate reactors for these two steps, including modifying theconditions in each reactor to facilitate the reactions in steps (x) and(y) respectively.

For example, step (x) can be carried out in the gas phase and step (y)in the liquid phase. A higher temperature can be used in step (x)compared to step (y). A higher pressure can be used in step (y) comparedto step (x).

Step (x) can be carried out in the absence of HF whereas HF can be usedas the fluorination agent in step (y). Alternatively, if HF is used instep (x), for example to stabilise the catalyst, it may be used in lowerconcentrations compared to step (y). For example, the molar ratio ofHF:organics (e.g. 243db) in step (x) preferably is from about 0.01:1 toabout 50:1, such as from about 0.1:1 to about 40:1, for example fromabout 0.5:1 to about 30:1 or about 2:1 to about 15:1 (e.g. from about10:1 to about 20:1 or from about 5:1 to about 10:1). The molar ratio ofHF:organics (e.g. 1233xf) in step (y) preferably is from about 1:1 toabout 100:1, such as from about 2:1 to about 50:1, for example fromabout 5:1 to about 40:1 (e.g. from about 10:1 to about 30:1).

When separate reactors are used, 1233xf produced in step (x) may betransferred from the first reactor directly to the second reactor forfluorination in step (y). Preferably, however, 1233xf is subjected to apurification step before being passed to the second reactor. Thepurification may be achieved by separation of the 1233xf from any otherproducts or reagents by one or more distillation, condensation or phaseseparation steps and/or by scrubbing with water or aqueous base.

In step (z), the compound of formula CF₃CFXCH₃ (wherein X═Cl or F) isconverted to 1234yf by dehydrochlorination of 244cb (i.e. wherein X═Cl)and/or dehydrofluorination of 245cb (i.e. wherein X═F).

Step (z) of the process of the invention may be carried out in anysuitable reactions conditions effective to dehydrohalogenate thecompound of formula CF₃CFXCH₃ to produce 1234yf. The dehydrohalogenationmay be carried out in the vapour and/or liquid phase and typically iscarried out at a temperature of from about −70 to about 1000° C. (e.g.about 0 to about 400° C.). Step (c) may be carried out at atmosphericsub- or super atmospheric pressure, preferably from about 0 to about 30bara.

The dehydrohalogenation may be induced thermally, may be base-mediatedand/or may be catalysed by any suitable catalyst. Suitable catalystsinclude metal and carbon based catalysts such as those comprisingactivated carbon, main group (e.g. alumina-based catalysts) andtransition metals, such as chromia-based catalysts (e.g. zinc/chromia)or nickel-based catalysts (e.g. nickel mesh).

One preferred method of effecting the dehydrohalogenation of thecompound of formula CF₃CFXCH₃ to produce 1234yf is by contactingCF₃CFXCH₃ with a metal catalyst, such as a chromia-based (e.g.zinc/chromia) catalyst.

When the catalyst used in step (y) is the same as in step (z) (e.g. whenusing a chromia-based catalyst such as a zinc/chromia catalyst), steps(y) and (z) may be carried out in a “one-pot” manner, i.e.simultaneously. Alternatively, when both steps (y) and (z) are carriedout in the presence of the same catalyst, the fluorination anddehydrohalogenation reactions may be carried out in two discrete steps,for example using two or more discrete reaction zones or reactors.

When both steps (y) and (z) are carried out in the presence of the samecatalyst, the reaction conditions for each step (y) and (z) may be thesame (e.g. in a one-pot process) or different. Preferably, the reactionconditions when steps (y) and (z) are carried out in the presence of thesame catalyst can be selected to be different so as to optimise thefluorination and dehydrohalogenation reactions, respectively. This isexplained in more detail below.

The preferred conditions for fluorination step (y) are set out above.Dehydrohalogenation step (z) may be carried out in the vapour or liquidphase, preferably the vapour phase. When conducted in the vapour phase,typically in the presence of a metal catalyst, such as a chromia-based(e.g. zinc/chromia) catalyst, step (z) preferably is conducted at atemperature of from about 200 to about 360° C., such as from about 240to about 340° C.

It is currently considered to be advantageous to use a higher pressurein step (y) (to promote fluorination) than in step (z) (to promotedehydrohalogenation). Thus, step (z) preferably is carried out fromabout 0.01 to about 25 bara or about 0.1 to about 20 bara, such as fromabout 1 to about 10 bara (e.g. 1 to 5 bara).

Fluorination step (y) preferably is carried out by contacting 1233xfwith HF. Step (z) of the invention may be carried out in the presence ofHF. For example residual HF from step (y) may be present, and/or HF froma separate feed. Alternatively, step (z) may be carried out in theabsence of HF, for example following separation of the compound offormula CF₃CFXCH₃ from HF prior to step (y), and with no additionalco-feed of HF. In certain embodiments it may be desirable to use some HFin order to prevent and/or retard excessive decomposition of the organicfeed and/or coking of the catalyst in step (z).

When both steps (y) and (z) are carried out in the presence of HF, themolar ratio of HF:organics can be selected to be different in each stepso as to promote fluorination in step (y) and dehydrohalogenation instep (z). For example, the molar ratio of HF:organics (e.g. the compoundof formula CF₃CFXCH₃) in step (z) preferably is from about 0.01:1 toabout 50:1, such as from about 0.1:1 to about 40:1, for example fromabout 0.5:1 to about 30:1 or about 2:1 to about 15:1 (e.g. from about10:1 to about 20:1 or from about 5:1 to about 10:1).

Another way of decreasing the concentration of HF in step (z) relativeto step (y) (thereby facilitating the fluorination/dehydrohalogenationreactions in these steps) is by adding a diluent gas (e.g. nitrogen) tostep (z).

Another preferred method of effecting the dehydrohalogenation of thecompound of formula CF₃CFXCH₃ to produce 1234yf is by contactingCF₃CFXCH₃ with a base (base-mediated dehydrohalogenation). Theconditions which may be used for base-mediated dehydrohalogenation step(z) broadly are the same as described above in relation to thedehydrohalogenation of the compound of formula CF₃CHFCH₂X in step (iii).

In a further embodiment, the subject invention provides a process forpreparing 3,3,3-trifluoropropene (1243zf), the process comprisingcontacting a compound of formula CX₃CH₂CH₂X or CX₃CH═CH₂, with hydrogenfluoride (HF) in the presence of a zinc/chromia catalyst, wherein each Xindependently is F, Cl, Br or I, provided that in the compound offormula CX₃CH═CH₂, at least one X is not F. Unless otherwise stated,this will be referred to hereinafter as the 1243zf preparation process(of the invention).

In a preferred embodiment, this process relates to the reaction of acompound of formula CX₃CH₂CH₂X to produce 1243zf.

The compound of formula CX₃CH₂CH₂X represents any halopropane whereinX═F, Cl, Br or I. In a preferred aspect, X═F or Cl. Examples ofcompounds of formula CX₃CH₂CH₂X include 1,1,1,3-tetrachloropropane(CCl₃CH₂CH₂Cl, 250fb), 1,1,3-trichloro-1-fluoropropane (CCl₂FCH₂CH₂Cl),1,3-dichloro-1,1-difluoropropane (CClF₂CH₂CH₂Cl),3-chloro-1,1,1-trifluoropropane (CF₃CH₂CH₂Cl, 253fb) and1,1,1,3-tetrafluoropropane (CF₃CH₂CH₂F, 254fb).

In one aspect, the compound of formula CX₃CH₂CH₂X is selected from250fb, 253fb and 254fb. In a preferred embodiment, the compound offormula CX₃CH₂CH₂X is 253fb. In a further preferred embodiment, thecompound of formula CX₃CH₂CH₂X is 254fb. In a particularly preferredembodiment, the compound of formula CX₃CH₂CH₂X is 250fb.

The compound of formula CX₃CH═CH₂ represents any halopropane whereinX═F, Cl, Br or I, provided that at least one X is not F. Preferably, Xis F or Cl (provided that at least one X is not F). Examples ofcompounds of formula CX₃CH═CH₂ include 3,3,3-trichloropropene(CCl₃CH═CH₂), 3,3-dichloro-3-fluoropropene (CCl₂FCH═CH₂) and3-chloro-3,3-difluoropropene (CClF₂CH═CH₂). In a preferred aspect, thecompound of formula CX₃CH═CH₂ represents 3,3,3-trichloropropene.

The inventors have unexpectedly found that zinc/chromia catalysts areparticularly effective for the fluorination and/or dehydrohalogenationreactions required by the 1243zf preparation process. In particular, thezinc/chromia catalysts are believed to be more active than othercatalysts, such as chromia-based catalysts. This enables the 1243zfpreparation process to be conducted using less forcing conditions (e.g.lower temperature and/or pressure) than would otherwise be necessary.

The zinc/chromia catalyst may be used in the 1243zf preparation processin an amount of from about 0.01 to about 50% by weight, such as fromabout 0.1 to about 30%, for example from about 0.5 to about 20%, basedon the combined weight of organics (e.g. compound of formula CX₃CH₂CH₂Xor CX₃CH═CH₂) and HF.

The 1243zf preparation process can be carried out in any suitableapparatus, such as a static mixer, a stirred tank reactor or a stirredvapour-liquid disengagement vessel. Preferably, the apparatus is madefrom one or more materials that are resistant to corrosion, e.g.Hastelloy® or Inconel®.

The 1243zf preparation process may be carried out batch-wise or (semi-)continuously. Preferably, the process of the invention is carried outcontinuously. Typically, the 1243zf preparation process is carried outin the vapour phase.

The process may be carried out at atmospheric, sub- or super atmosphericpressure, typically at from 0 to about 30 bara, preferably from about 1to about 20 bara.

Typically, the 1243zf preparation process of the invention is carriedout a temperature of from about 100° C. to about 500° C. (e.g. fromabout 150° C. to about 500° C. or about 100 to about 450° C.).Preferably, the process is conducted at a temperature of from about 150°C. to about 450° C., such as from about 150° C. to about 400° C., e.g.from about 200° C. to about 350° C. Lower temperatures may also be usedin the process of the invention, for example in the conversion of 250fbto 1243zf, such as from about 150° C. to about 350° C., e.g. from about150° C. to about 300° C. or from about 150° C. to about 250° C.

The 1243zf preparation process typically employs a molar ratio ofHF:organics of from about 1:1 to about 100:1, such as from about 3:1 toabout 50:1, e.g. from about 4:1 to about 30:1 or about 5:1 or 6:1 toabout 20:1 or 30:1.

The reaction time for the 1243zf preparation process generally is fromabout 1 second to about 100 hours, preferably from about 10 seconds toabout 50 hours, such as from about 1 minute to about 10 or 20 hours. Ina continuous process, typical contact times of the catalyst with thereagents is from about 1 to about 1000 seconds, such from about 1 toabout 500 seconds or about 1 to about 300 seconds or about 1 to about50, 100 or 200 seconds.

The 1243zf preparation process is particularly effective for preparing3,3,3-trifluoropropene (1243zf) by contacting 1,1,1,3-tetrachloropropane(250fb) with hydrogen fluoride (HF) in the presence of a zinc/chromiacatalyst.

250fb may be purchased from common suppliers of halogenatedhydrocarbons, such as Apollo Scientific, Stockport, UK. Alternatively,250fb may be prepared by the telomerisation of carbon tetrachloride(CCl₄) and ethylene (see, for example, J. Am. Chem. Soc. Vol. 70, p2529, 1948, which is incorporated herein by reference).

The conversion of 250fb to 1243zf typically involves fluorination anddehydrohalogenation sub-steps.

For example, 250fb may be fluorinated to produce a compound of formulaCX₃CH₂CH₂Cl (wherein X═Cl or F), as illustrated in the scheme below.1243zf may be produced by a final dehydrochlorination step of thecompound of formula CX₃CH₂CH₂Cl wherein X═F. This is illustrated belowas route (a).

Alternatively, 250fb may be dehydrochlorinated to produce3,3,3-trichloropropene, followed by step-wise fluorination to produce1243zf. This is illustrated above as route (b). Routes (a) and (b)correspond to routes (b1) and (b2), respectively, as described herein inrelation to step (b) of the process of the invention.

Either or both routes (a) and (b) may be operable to convert 250fb to1243zf. For example, CCl₂FCH₂CHCl in route (a) may be dehydrochlorinatedto produce CCl₂FCH═CH₂ in route (b). It is anticipated that some ofthese reactions may occur spontaneously if HF and 250fb are mixed atelevated temperatures, but the reaction will not go to completion in theabsence of a zinc/chromia catalyst in any reasonable timescale.

Surprisingly, the inventors have found that zinc/chromia catalysts areeffective at facilitating the one-pot conversion of 250fb and HF to1243zf. In particular, the activity of the catalyst is believed to allowless forcing conditions (e.g. lower temperatures) compared to known(vapour phase) processes for producing 1243zf, whilst maintainingexcellent conversion of 250fb and selectivity to 1243zf.

The invention will now be illustrated by the following non-limitingExamples.

EXAMPLE 1 Chlorination of 3,3,3-trifluoropropene (1243zf) at atmosphericpressure

1.1 g of activated carbon catalyst was loaded into a 1.25 cm (0.5″)×30cm Inconel reactor tube. The catalyst was dried under flowing nitrogen(c.a. 10 ml/min) at 250° C. for 2 hours. The tubes were then cooled tothe reaction temperatures shown in Tables 1a and 1b below prior tostarting the feed flows, chlorine (c.a. 2 ml/min) and 1243zf (c.a. 6ml/min). Samples of the reaction gases exiting the reactor zone weretaken and analysed by GC and GC-MS (see Table 1b). An additional seriesof experiments were conducted using an empty tube containing no catalyst(see Table 1a).

TABLE 1A (no catalyst): N₂ = 9 ml/min; Cl₂ = 2 ml/min, 1243zf = 6 ml/minTem- 1243zf per- Con- 1233 ature version 1243zf total* 1223xd 243db1213xa Minors ° C. (%) (mol %) (mol %) (mol %) (mol %) (mol %) (mol %)50 2.4 97.6 1.4 0.3 0.2 0.0 0.6 100 0.7 99.3 0.3 0.1 0.1 0.0 0.2 150 0.799.3 0.3 0.0 0.2 0.0 0.1 200 0.7 99.3 0.1 0.0 0.4 0.0 0.1 250 2.1 97.91.2 0.1 0.7 0.0 0.2

TABLE 1B (1.1 g activated carbon): N₂ = 10 ml/min; Cl₂ = 2 ml/min;1243zf = 6 ml/min Tem- 1243zf per- Con- 1233 ature version 1243zf total*1223xd 243db 1213xa Minors ° C. (%) (mol %) (mol %) (mol %) (mol %) (mol%) (mol %) 100 16.5 83.5 9.8 0.2 5.2 0.0 1.3 125 40.7 59.3 1.8 0.6 37.90.0 0.4 150 64.8 35.2 10.8 0.2 52.2 0.0 1.5 175 74.1 25.9 18.8 0.8 47.00.6 6.9 200 65.0 35.0 29.6 2.6 20.2 1.8 10.9 250 74.7 25.3 66.4 1.7 3.00.1 3.6 *Includes both 1233 isomers CF₃CCl═CH₂ (1233xf) and CF₃CH═CClH(1233zd) 1223xd = CF₃CCl═CHCl

1213xa ═CF₃CCl═CCl₂ EXAMPLE 2 Chlorination of 3,3,3-trifluoropropene(1243zf) at atmospheric pressure

4.0 g of activated carbon catalyst was loaded into a 1.25 cm (0.5″)×30cm Inconel reactor tube. The catalyst was dried under flowing nitrogen(c.a. 30 ml/min) at 250° C. for 1.5 hours. The tube was then cooled tothe reaction temperatures shown in the Table below prior to starting thefeed flows nitrogen (0 or 8 ml/min), chlorine (8 ml/min) and 1243zf (8ml/min). Samples of the reaction gases exiting the reactor zone weretaken and analysed by GC and GC-MS.

TABLE 2 Feed flows and conditions 1243zf 8 8 8 8 8 (mls/min) Cl₂ 8 8 8 88 (mls/min) N₂ 8 0 0 0 0 (mls/min) Reactor 150 150 175 185 200Temperature (° C.) Reactor off-gas analysis (mol %) 1243zf 14.43 5.485.04 17.60 22.70 1233xf 28.11 33.49 48.29 61.89 50.94 1233zd 0.43 0.210.19 2.09 2.20 1223xd 1.29 0.80 0.87 5.00 7.52 1213xa 0.02 0.02 0.030.36 0.75  243db 50.61 55.24 37.66 9.59 9.81 Unknown 5.11 4.76 7.92 3.496.08 Total

Comparison of the results in Tables 1b and 2 with the results in Table1a shows that activated carbon is a surprisingly effective catalyst forthe conversion of 1243zf to 243db (and the onward conversion of 243db to1233xf).

EXAMPLE 3 Single stage chlorofluorination of 3,3,3-trifluoropropene(1243zf)

A 1.25 cm (0.5″)×30 cm Inconel reactor tube loaded with 4 g 5.2%zinc/chromia catalyst. The catalyst was dried under flowing nitrogen (50ml/min) for 2 hours at 250° C. After the drying time, HF (5-8 ml/min)was introduced into the nitrogen stream to begin fluorination of thecatalyst. The temperature was ramped to 380° C. at 40° C./min and heldthere for 16 hours. After 2-3 hours HF breakthrough was detected in thereactor off-gas and the nitrogen flow was switched off. After thistreatment the reactor temperature was reduced to the temperaturesindicated in Table 3 and a mixture comprising HF (12 ml/min), 1243zf(3.2 ml/min) and chlorine (3 ml/min) passed through it. Samples of thereactor off-gas were taken and analysed by GC and GC-MS. The GC wascalibrated using known standards to determine response factors and anaverage response factor was used to quantify unknowns.

TABLE 3 (4 g Zn/Cr catalyst): HF = 12 ml/min; 1243zf = 3.2 ml/min; Cl₂ =3 ml/min Temperature ° C. Product (mol %) 200 220 240 280 300 320 3501243zf 49.0 54.9 61.8 65.2 65.9 55.8 30.9 1233xf 5.7 12.5 21.1 29.1 30.537.7 45.2 1223xd 12.8 9.8 4.5 1.0 0.5 0.4 0.0  243db 32.6 22.6 12.2 2.71.4 1.6 4.7 Others including 0.0 0.2 0.3 1.9 1.6 4.6 19.2 1234yf

Comparison of the results in Tables 1a and 2 shows that zinc/chromia isa surprisingly effective catalyst for the conversion of 1243zf to 243db(and the onward conversion of 243db to 1233xf).

EXAMPLE 4 Single Stage Dehydrohalogenation of CF₃CFHCH₂F (245eb) to1234yf

A 1.25 cm (0.5″)×30 cm Inconel reactor tube loaded with 4 g 5.2%zinc/chromia catalyst. The catalyst was dried under flowing nitrogen (50ml/min) for 2 hours at 250° C. After the drying time, HF (5-8 ml/min)was introduced into the nitrogen stream to begin fluorination of thecatalyst. The temperature was ramped to 380° C. at 40° C./min and heldthere for 16 hours. After 2-3 hours HF breakthrough was detected in thereactor off-gas and the nitrogen flow was switched off. After thistreatment the reactor temperature was reduced to the temperatures shownin Table 4 and a mixture comprising nitrogen and 245eb passed over it.Samples of the reactor off-gas were taken and analysed by GC and GC-MS.The GC was calibrated using known standards to determine responsefactors and an average response factor was used to quantify unknowns.

TABLE 4 Nitrogen flow 8 ml/min, 245eb flow 2 ml/min Tem- perature ° C.Product 200 225 250 275 300 325 350 375 400 1234yf 0.4 0.9 2.4 17.7 40.751.8 88.8 96.4 100.0 1243zf 0.1 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0  245eb99.2 97.2 93.2 71.2 59.2 48.2 2.9 0.0 0.0  245cb 0.2 1.7 4.3 11.1 0.00.0 8.2 3.6 0.0

The results in Table 3 show that zinc/chromia is a surprisinglyeffective catalyst for the dehydrofluorination of 245eb to 1234yf.

EXAMPLE 5 Hydrofluorination of 250fb (CCl₃CH₂CH₂Cl) at Elevated Pressure

The reactor, made from an Inconnel tube 30 cm×0.5 inches, was chargedwith 6 g of a 5.2% Zn/Chromia catalyst which was essentially amorphousin character, which was treated as follows:

The catalyst was first dried by heating under nitrogen (80 ml/min) at250° C. and 3 barg for 48 hours. Next, pre-fluorination of the catalystwas begun by introducing HF (4 ml/min) into the nitrogen stream andincreasing the temperature to 300° C. for 16 hours. During the last 5hours the nitrogen flow was reduced steadily to zero. The temperaturewas then ramped to 380° C. at 25° C./hr and held at 380° C. for 7 hoursand then cooled to 250° C. at 25° C./hr.

A feed mixture comprising 250fb (3 ml/min) and HF (45 ml/min) was thenpassed over the catalyst at 15 barg and 200° C. The gases exiting thereactor were periodically sampled and analysed by GC after passingthrough an alkaline scrubber to remove acid gases. The only productsdetected in the reactor off-gases following removal of the acid gaseswere the desired product 1243zf (91 mol %, CF₃CH═CH₂) and1,1-difluoro-1,3-dichloropropane (9 mol %, CF₂ClCH₂CH₂Cl).

It is believed that the 1,1-difluoro-1,3-dichloropropane could beconverted to 1243zf by altering the reaction conditions (e.g. byincreasing the temperature and/or contact time). In this way, 250fbcould be fully converted in 100% selectivity to 1243zf in a single pass.

EXAMPLE 6 Hydrofluorination of 250fb (CCl₃CH₂CH₂Cl) at AtmosphericPressure

The reactor, made from an Inconnel tube 30 cm×0.5 inches, was loadedwith 2.0 g of a 5.2% wt Zn on chromia catalyst which was essentiallyamorphous in character. The catalyst was then dried under nitrogen (80ml/min) at 250° C. for 3 hours. HF (20 ml/min) was then introduced intothe nitrogen flow and pre-fluorination of the catalyst commenced. WhenHF was detected in the reactor off-gases the reactor temperature wasramped from 250° C. to 370° C. at 25° C./hr and maintained there for 7hours before being cooled back to 200° C. at 25° C./hr.

A feed mixture comprising 250fb (1 ml/min), HF (25 ml/min) and nitrogen(30 ml/min) was fed to the reactor at 200° C. for a total of 15 hours.The gases exiting the reactor were scrubbed with a an alkaline solutionto remove acid gases and analysed by GC-MS and GC. The only speciesidentified in the scrubbed reactor off-gases throughout the wholeexperiment was 1243zf.

Examples 5 and 6 demonstrate that the reaction of 250fb with HF using azinc/chromia catalyst selectively produces 1243zf under very mildconditions.

EXAMPLE 7 Vapour Phase Conversion of 254fb (CF₃CH₂CH₂F) to 1243zf(CF₃CH═CH₂)

The reactor, made from an Inconnel tube 30 cm×0.5 inches was loaded with2.0 g of a 5.2% wt Zn on chromia catalyst which was essentiallyamorphous in character. The catalyst was then dried under nitrogen (80ml/min) at 250° C. for 3 hours. HF (20 ml/min) was then introduced intothe nitrogen flow and pre-fluorination of the catalyst commenced. WhenHF was detected in the reactor off-gases the reactor temperature wasramped from 250° C. to 370° C. at 25° C./hr and maintained there for 7hours before being cooled back to 200° C. at 25° C./hr.

Mixtures of HF and 254fb were then fed across the catalyst at varioustemperatures and ratio's to demonstrate the conversion of 254fb to1243zf. Nitrogen carrier gas flows were used to aid delivery of thefeeds to the reactor. The gases exiting the reactor were analysed byGC-MS and GC. The results are summarised in the Table below:

Temperature (° C.) 200 225 250 200 225 250 275 300 300 225 250 254fbfeed 13.5 12.1 16.7 20.4 22.9 10.6 12.8 10.0 1.0 4.9 4.9 (ml/min) HFfeed 27.9 27.9 27.6 34.3 35.3 35.4 35.2 35.6 35.3 0 0 (ml/min) Ratio 2.12.3 1.7 1.7 1.5 3.3 2.8 3.6 35.4 N/A N/A HF:254fb Total N₂ flow 10.110.1 10.1 10.1 10.1 10.1 10.1 10.1 10.1 5 5 (ml/min) ROG* 254tb 93.350.1 14.8 93.3 71.9 17.4 1.5 0.1 0.7 1.3 0.1 (mol %) ROG* 6.7 49.9 85.26.7 28.1 82.6 98.5 99.9 99.3 98.7 99.9 1243zf (mol %) *ROG = ReactorOff-gas composition

As can be seen the conversion of 254fb to 1243xf is clean and facileover a zinc/chromia catalyst at moderate conditions.

1. A process for preparing 1,1,1-trifluoro-2,3-dichloropropane (243db),which process comprises (i) contacting 3,3,3-trifluoropropene (1243zf)with chlorine in the presence of a catalyst, wherein the catalystcomprises activated carbon, alumina and/or an oxide of a transitionmetal.
 2. A process according to claim 1 wherein the process isconducted at a temperature of from about −100 to about 400° C. and apressure of from 0 to about 30 bara.
 3. A process according to claim 1wherein the molar ratio of 1243zf:chlorine is from about 10:1 to about1:5.
 4. (canceled)
 5. A process according to claim 1 comprising the step(b) of converting 1,1,1,3-tetrachloropropene to produce the3,3,3-trifluoropropene (1243zf).
 6. A process according to claim 5comprising the step (a) of telomerising ethylene and carbontetrachloride (CCl₄) to produce the 1,1,1,3-tetrachloropropene. 7.(canceled)
 8. A process according to claim 6 wherein step (a) comprisescontacting ethylene with CCl₄ in the liquid and/or vapour phase in thepresence of a catalyst in an amount of from about 0.01 to about 50 mol%.
 9. A process according to claim 8 wherein step (a) the catalystcomprises iron, copper and/or peroxide.
 10. A process according to claim6 wherein step (a) the molar ratio of CCl₄:ethylene is from about 1:1 toabout 50:1.
 11. A process according to claim 6 wherein step (a) isconducted at a temperature of from about 20 to about 300° C. and apressure of from 0 to about 40 bara.
 12. A process according to claim 6wherein the 1,1,1,3-tetrachloropropane is purified before conversion to3,3,3-trifluoropropene (1243zf)
 13. A process according to claim 5wherein step (b) comprises fluorination of 1,1,1,3-tetrachloropropene toproduce a compound of formula CF₃CH₂CH₂Cl (253fb), followed bydehydrohalogenation of the 253fb to produce 1243zf.
 14. A processaccording to claim 13 comprising contacting 1,1,1,3-tetrachloropropenewith HF in the presence of a catalyst (e.g. a zinc/chromia catalyst) toproduce 1243zf.
 15. A process according to claim 5 wherein step (b) iscarried out at a temperature of from about 20 to about 500° C. and apressure of from 0 to about 30 bara.
 16. A process according to claim 14wherein step (b) the molar ratio of HF:organics is from about 1:1 toabout 100:1.
 17. (canceled)
 18. A process according to claim 1 furthercomprising the step of (ii) contacting the 243db with hydrogen fluoride(HF) in the presence of a fluorination catalyst to produce the compoundof formula CF₃CHFCH₂X
 19. A process according to claim 18, wherein steps(i) and (ii) are conducted simultaneously.
 20. A process according toclaim 19 wherein the molar ratio of HF:1243zf is from about 1:1 to about200:1.
 21. A process according to claim 18 wherein step (ii) is carriedout subsequent to step (i).
 22. A process according to claim 21 whereinthe 243db formed in step (i) is separated and/or purified prior tofluorination in step (ii).
 23. A process according to claim 21 whereinthe fluorination catalyst in step (ii) is a chromia catalyst, preferablya zinc/chromia catalyst.
 24. A process according to claim 21 whereinstep (i) is conducted in the absence of HF.
 25. A process according toclaim 21 wherein step (i) is conducted in the presence of HF, whereinthe molar ratio of HF:1243zf is from about 0.01:1 to about 10:1.
 26. Aprocess according to claim 18 wherein the molar ratio of HF:243db isfrom about 1:1 to about 100:1.
 27. A process according to claim 21wherein step (i) is conducted at a temperature of from about −100 toabout 400° C. and a pressure of from about 0.1 to about 20 bara, andstep (ii) is conducted at a temperature of from about 100 to about 380°C. and a pressure of from about 5 to about 28 bara.
 28. A processaccording to claim 18 wherein steps (i) and (ii) are both carried out inthe vapour phase.
 29. A process according to claim 18 wherein step (i)is carried out in the liquid phase and step (ii) is carried out in thevapour phase.
 30. A process according to claim 18 comprising the step(iii) of dehydrohalogenating the compound of formula CF₃CHFCH₂X toproduce a 2,3,3,3-tetrafluoropropene (1234yf).
 31. (canceled)
 32. Aprocess according to claim 16 comprising the step (x) of converting the243db to 3,3,3-trifluoro-2-chloroprop-1-ene (CF₃CCl═CH₂, 1233xf). 33.(canceled)
 34. A process according to claim 32 wherein step (x) iscarried out in the presence of a catalyst selected from catalystscomprising activated carbon, catalysts comprising alumina, catalystscomprising an oxide of a transition metal, lewis acid metal halidecatalysts and mixtures thereof.
 35. A process according to claim 32wherein step (x) is carried out at a temperature of from about −70 toabout 450° C. and a pressure of from 0 to about 30 bara.
 36. A processaccording to claim 32 comprising the step (y) of contacting the 1233xfwith a fluorinating agent to produce a compound of formula CF₃CFXCH₃,wherein X═Cl or F.
 37. (canceled)
 38. A process according to claim 36wherein step (y) is carried is carried out at a temperature of fromabout −100 to about 400° C. and a pressure of from 0 to about 50 bara.39. A process according to claim 36 wherein the fluorinating agent ishydrogen fluoride (HF).
 40. A process according to claim 36 wherein step(y) is carried out in the presence of a catalyst selected from catalystscomprising activated carbon, catalysts comprising alumina, catalystscomprising an oxide of a transition metal, lewis acid metal halidecatalysts and mixtures thereof.
 41. A process according to claim 36wherein steps (x) and (y) are conducted in separate reactors.
 42. Aprocess according to claim 36 wherein step (x) is carried out in thevapour phase.
 43. A process according to claim 42 wherein step (y) iscarried out in the presence of a catalyst selected from catalystscomprising activated carbon, alumina and/or an oxide of a transitionmetal.
 44. A process according to claim 42 wherein step (y) is carriedout at a temperature of from about 0 to about 390° C. and a pressure offrom 0.1 to about 30 bara, preferably at a temperature of from about 200to about 370° C. and a pressure of from about 1 to about 10 bara.
 45. Aprocess according to claim 36 wherein step (x) is carried out in theliquid phase.
 46. A process according to claim 45 wherein step (y) iscarried out in the presence of a lewis acid metal halide catalyst.
 47. Aprocess according to claim 45 wherein step (y) is carried out at atemperature of from about −50 to about 250° C. and a pressure of fromabout 1 to about 50 bara, preferably at a temperature of from about 10to about 150° C. and a pressure of from about 10 to about 30 bara.
 48. Aprocess according to claim 32 wherein step (x) is conducted in thepresence of HF.
 49. A process according to claim 48 wherein the molarratio of HF:organics in step (x) is from about 0.01:1 to about 50:1,preferably from about 2:1 to about 15:1.
 50. A process according toclaim 39 wherein the molar ratio of HF:organics in step (y) is fromabout 1:1 to about 100:1, preferably from about 5:1 to about 40:1.
 51. Aprocess according to claim 36 comprising the step (z) ofdehydrohalogenating the compound of formula CF₃CFXCH₃ to produce 1234yf.52. (canceled)
 53. A process according to claim 51 wherein thedehydrohalogenation step (z) is carried out at a temperature of from −70to 1000° C. and a pressure of from 0 to about 30 bara.
 54. A processaccording to claim 51 wherein step (z) is carried out by metal catalyseddehydrohalogenation.
 55. A process according to claim 54 wherein step(z) is carried out at a temperature of from about 0 to about 400° C. anda pressure of from 0.01 to about 25 bara, preferably from about 200 toabout 360° C. and from about 1 to about 10 bara.
 56. A process accordingto claim 54 wherein step (z) is conducted in the presence of HF.
 57. Aprocess according to claim 56 wherein the wherein the molar ratio ofHF:organics in step (z) is from about 0.01:1 to about 50:1, preferablyfrom about 2:1 to about 15:1.
 58. A process according to any of claim 54wherein step (z) is carried out simultaneously with step (y).
 59. Aprocess according to claim 51 wherein step (z) is carried out bycontacting the compound of formula CF₃CFXCH₃ with a base.
 60. A processaccording to claim 59 wherein (z) is carried out at a temperature offrom about −50 to about 300° C., preferably from about 20 to about 250°C.
 61. A process according to claim 59 wherein the base is selected fromthe group consisting of: a metal hydroxide, including alkali metalhydroxides, sodium hydroxide and potassium hydroxide; alkaline earthmetal hydroxide, including calcium hydroxide a metal amide and mixturesthereof. 62-63. (canceled)
 64. A process according to claim 59 whereinstep (z) is carried out in a solvent, preferably wherein the solvent isselected from water, alcohols, diols, polyols, polar aprotic solventsand mixtures thereof, and wherein the process optionally is carried outin the presence of a co-solvent or diluent.
 65. A process according toclaim 59 wherein step (z) is carried out in the presence of a catalyst,preferably wherein the catalyst is a crown ether or a quaternaryammonium salt.
 66. A process for preparing 3,3,3-trifluoropropene(1243zf), the process comprising contacting a compound of formulaCX₃CH₂CH₂X or CX₃CH═CH₂, with hydrogen fluoride (HF) in the presence ofa zinc/chromia catalyst, wherein each X independently is F, Cl, Br or I,provided that in the compound of formula CX₃CH═CH₂, at least one X isnot F.
 67. A process according to claim 66 wherein X is F or Cl.
 68. Aprocess according to claim 66, wherein the process comprises contactinga compound of formula CX₃CH₂CH₂X.
 69. A process according to claim 66wherein the compound of formula CX₃CH₂CH₂X comprises CF₃CH₂CH₂Cl(253fb).
 70. A process according to claim 66 wherein the compound offormula CX₃CH₂CH₂X comprises CCl₃CH₂CH₂Cl (250fb).
 71. A processaccording to claim 66 wherein the process is conducted at a temperatureof from about 100° C. to about 500° C., preferably from about 150° C. toabout 450° C.
 72. A process according to claim 66 wherein the process isconducted at a pressure of from 0 to about 30 bara, preferably fromabout 1 to about 20 bara.
 73. A process according to claim 66 whereinthe molar ratio of HF:organics is from about 1:1 to about 100:1,preferably from about 3:1 to about 50:1.
 74. A process according toclaim 66 wherein the process is conducted in the vapour phase.
 75. Aprocess according to claim 66 wherein the process is continuous orsemi-continuous. 76-77. (canceled)